DESCRIPTION: Structure and function of A1 heterogeneous nuclear ribonuclear protein (hnRNP) will be studied. This is an abundant protein that binds pre-mRNA. There is disagreement in the literature over whether or not it binds sequence specifically. One goal of this project is to measure the sequence specificity of binding using an equilibrium titration method developed in this lab. The effects of posttranslational modifications, such as methylation and phosphorylation on binding, will also be studied. "A major effort....will be to solve the structure of an A1:RNA complex." Both x-ray crystallography and NMR methods will be tried. The effect on binding of the length of linker arms connecting two RNA binding domains will also be studied and compared with theory developed by Crothers. A yeast two-hybrid system will be used to identify proteins that interact with A1. The sequence specificity of RNA binding and the proteins that bind should provide insight into the function of A1, including how it modulates selection of alternative 5'-splice sites. Some conclusions may be relevant to the more than 100 other RNA binding proteins that use the same RNA binding motif as A1.